President Muhammadu Buhari, a former military ruler, took office last year after pledging in his election campaign to crack down on corruption and defeat Boko Haram, which has killed more than 15,000 people and displaced about two million in the last seven years.

Military procurement over the last few years is being investigated by the country's Economic and Financial Crimes Commission (EFCC).

A committee recommended the "further investigation" of 18 serving and retired military personnel, 12 serving and retired public officials and 24 chief executive officers of companies involved in arms deals.

Mohammed said findings released by the Presidential Committee on the Audit of Defence Equipment, which said contracts awarded by the army had been "characterized by lack of due process" and were "tainted by corrupt practices", covered the period from 2011 to 2015.

"The irregularities in the awards ensured that the military did not get value for money, with very serious consequences," Mohammed said in a statement, adding a total of $685,349,692 was spent on procurement and operations in the period.

Mohammed did not respond to phone calls and a text message asking him to elaborate on the "serious consequences".

Boko Haram took over a swathe of northeast Nigeria in 2014 in its attempt to create an Islamic state adhering to strict sharia law.

Nigeria's army, aided by troops from neighboring countries, has recaptured most of the territory but the jihadist group, which last year pledged loyalty to Islamic State, still regularly stages suicide bombings.

The committee was set up to carry out an audit of arms and equipment procurement from 2007 to 2015. Mohammed said the period from 2007 to 2010 would be assessed when documents were available.